As a light source of a vehicular lamp, a semiconductor light source such as, for example, a light emitting diode (LED) or a semiconductor laser, is being used, in lieu of a conventional bulb such as, for example, an incandescent bulb. Such a semiconductor light source has various advantages, such as for example, a variety of designs through a combination with light guides or high power saving, as compared to a bulb. See, for example, Japanese Patent Laid-Open Publication No. 2003-141909 and Japanese Patent Laid-Open Publication No. 2005-347144.